A polymer (resin) has been used, for example, in molding materials, layer forming materials or adhesives of electronics parts, optical products, optical parts, and the like. The polymer (resin) is formed by a polymerization reaction of forming a polymer chain by bonding polymer precursors (monomers) or by a cross-linking reaction of linking polymer chains, by using a polymerization initiator, and physical and chemical properties thereof are different from those of the polymer precursors (monomers) in many cases.
To form a structure, where molecules are linked two-dimensionally or three-dimensionally by this polymerization reaction or cross-linking reaction is named curing, and there has been known curing by a polymerization initiator which is sensitive to light (active energy rays) such as infrared rays, visible rays, UV rays and X-rays (hereafter it may be abbreviated as photo-curing), curing by a polymerization initiator which is sensitive to heat (hereafter it may be abbreviated as thermal-curing), and the like.
The polymerization initiators to be used in curing are classified largely into three groups; a radical generator, an acid generator and a base generator, depending on active species generated. The radical generator is a polymerization initiator generating radical species by irradiation of light (active energy rays) or by heating, which has conventionally been used widely, however, it has the drawbacks that the radical species are inactivated by oxygen in air, and then the polymerization reaction is inhibited and suppressed. Accordingly, in using the radical generator, special devise is needed, such as interception of oxygen in air. The acid generator is a polymerization initiator generating an acid by irradiation of light (active energy rays) or by heating, and does not receive inhibition by oxygen, therefore a wide variety of acid generators have been provided practically since the latter half of 1990's. However, there may be the case where the acid generated may remain inside a system even after curing, and thus there has been pointed out a problem such as decreasing film performance caused by denaturation of a cured film by influence of the remaining acid after curing a curing composition containing the acid generator, or a problem of corrosion by the acid to a metal wiring on a semiconductor substrate. On the other hand, the base generator is a generator which generates a base by irradiation of light (active energy rays) or by heating, and does not receive inhibition by oxygen in air, and the problem of corrosion or denaturation of a cured film in the case of using an acid generator is hardly occurred, and thus research and development thereof have been carried out actively in recent years.
Recently, the technology of applying a photosensitive composition containing a photo-base generator to a photoresist material, a photo-curing material, and the like, has been investigated. For example, there has been proposed a method for generating amines within an epoxy resin by irradiation of light (active energy rays), and then curing the epoxy resin by heating treatment, by utilization of the fact that, for example, a compound having an epoxy group is cured by generation of a cross-linking reaction by an action of a base (for example, NON PATENT LITERATURE 1).
In the case of curing an epoxy-based compound by amines generated from a base generator, a weak base, such as a primary amine and a secondary amine, requires a long period of time in reaction with an epoxy group, and thus it has required heating treatment at high temperature and the like to increase curing speed. In addition, although it is possible to increase curing speed by increasing cross-linking density using a multi-functionalized primary amine or secondary amine, it is necessary for all amines to be made latescent (protection) by carrying out salt formation to all amines, and it could have been to decrease solubility significantly. In this way, in the case where a base generated from a base generator is a weak base, there was a problem that curing of an epoxy-based compound cannot be carried out simply, conveniently and efficiently.
On the contrary, it has been reported that in the case of a base generator which generates strongly basic amines, such as a tertiary amine, an amidine, a guanidine and a phosphazene, these amines are easy to function as catalysts, therefore it is capable of curing an epoxy-based compound even in relatively small amount, and particularly in the case where a cross-linking agent having an acidic proton (for example, a multifunctional carboxylic acid, a multifunctional phenol, a multifunctional thiol, a multifunctional β-keto-ester, and the like) is used in combination, the epoxy-based compound can be cured rapidly under low temperature condition.
As the base generator of such amines, there have conventionally been known a photo-base generator, such as an amineimide-based compound which generates a tertiary amine, an amidine [such as 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), 1,8-diazabicyclo[5.4.0]-7-undecene (DBU)], imidazole, pyridine, and the like, by irradiation of light (active energy rays) (for example, PATENT LITERATURE 1); and an ammonium borate-based compound (for example, PATENT LITERATURE 2, NON-PATENT LITERATURE 2, NON-PATENT LITERATURE 3, NON-PATENT LITERATURE 4, NON-PATENT LITERATURE 5). In addition, there have also been known examples of a compound composed of a carboxylic acid which is decarboxylated by irradiation of light (active energy rays) and amines (for example, PATENT LITERATURE 3); a benzoic acid-based compound which is circularly esterified by irradiation of light (active energy rays) (for example, PATENT LITERATURE 4); a tetraphenylborate-based compound which generates a strong base, such as guanidine, for example, 1,1,3,3-tetramethylguanidine (TMG), 1,5,7-triazabicyclo[4.4.0]deca-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene (MTBD), and the like, and phosphazene, by irradiation of light (active energy rays) (for example, NON-PATENT LITERATURE 6); a tetraarylborate-based compound which generates a proazaphosphatrane which is a strong base, such as 2,8,9-triisopropyl-2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane, by irradiation of light (active energy rays) (for example, NON-PATENT LITERATURE 7). Still more, there has also been known a compound which generates biguanides, as an organic strong base having higher basicity than amidines or guanidines (for example, PATENT LITERATURE 5, NON-PATENT LITERATURE 8, NON-PATENT LITERATURE 9), and there has also been reported an example of using a compound which generates such biguanides for curing an epoxy (for example, PATENT LITERATURE 6). In addition, there has also been known an example of applying a compound which is obtained by forming a salt by a pyrolytic compound together with biguanides, as a thermal-curing catalyst (for example, PATENT LITERATURE 7, PATENT LITERATURE 8).
However, although the base generators are capable of generating strong bases, they are generally solids in many cases, and most of them had a problem of having insufficient solubility to an organic solvent. In addition, in the case of a base generator composed of, for example, a carboxylic acid and amines, there are some oil-like compounds not having the problem of solubility in an organic solvent, depending on a combination thereof, however, such a base generator generally has a problem that heat resistance is inferior.
Under such a circumstance, the present inventors have reported a base generator composed of a carboxylic acid having a specific structure and biguanides as a base generator which is capable of generating strong bases (biguanides), having high solubility in various organic solvents and base-reactive compounds, and having high heat resistance (PATENT LITERATURE 9).